Atom interferometers use the wave character of atoms as a technique for precision measurements in geodesy, inertial navigation, time, and fundamental physics. Atom interferometry is typically performed by manipulating quantum objects, such as atoms, by applying one or more sequences of coherent beam splitting sequences. After being split into two parts by a coherent beam-splitting process, the atomic wavepackets move along two different paths for an interrogation time, during which the two atomic wavepackets accumulate different phases.
Some of the most precise measurements of physical quantities currently available derive from atomic interferometry. These include limits on composition-dependent gravitational forces (Einstein's principle of equivalence), measurements of the ratio
  ℏ  min an atom, and derivative determinations of the fine structure constant. Measurements of such exquisite precision require stability in the face of external factors such as temperature or pressure variations and other mechanical or optical perturbations.
Certain types of atom interferometers employ the use of multiple, spatially separated, parallel laser beams for producing the interferometer interaction. Maintaining parallel alignment of these laser beams is often critical for proper operation of the device, since loss of parallelism can result in sensors drift and/or loss of signal. Typical separated beam atom interferometer systems rely on mirrors, beam splitters, and retro-reflectors to implement parallel sets of laser beams. The alignment of these systems can be affected by any one of a number of different external factors, including temperature variation and system perturbation.
A comprehensive review of atomic interferometers may be found in Cronin, et al., “Optics and Interferometry with Atoms and Molecules,” Rev. Mod. Phys., vol. 81, pp. 1051-129 (2009), which is incorporated herein by reference. A particular example is provided by Erickson, “Construction of a Calcium Matter-Wave Interferometer,” Masters Dissertation, Brigham Young University (2007) (hereinafter, “Erickson”), which is incorporated herein by reference. Erickson points out that mechanical and thermal vibrations in the optics preceding the cavity are written onto the laser light as noise. (Erickson, p. 64) The remedy provided by Erickson is to place the optics inside a 1-inch thick aluminum enclosure. Beam steering, as shown in Erickson's FIG. 4.1, is achieved by means of prism reflectors and flat mirrors separately mounted on kinetic tilt mounts.
Configurations in which external factors may bear on the angle at which successive laser beams impinge on a probed atomic ensemble, such as a beam of thermal atoms, are prone to measurement perturbations and drift that may ultimately limit system sensitivity. Thus, a configuration that would, by its nature, cancel such perturbations and drift, is particularly valuable. Such a configuration is taught for the first time herein.